1. Field of the Invention
The present invention relates to a corner construction for rectangular extruded metal tubing or the like, and more particularly to an improved corner useful in the manufacture of doors and windows.
2. Description of the Prior Art
A large industry presently exists in the United States and other countries for the manufacture of doors, windows, structural frames, and similar structures in which the elements thereof are formed of extruded metal. In particular, it is common to utilize extruded aluminum of a hollow cross-section having a generally rectangular shape for such structures. These extruded metal shapes are cut to required lengths and assembled to form a rectangular or square frame for doors, windows, and the like. Conventionally, the practice has been to cut the ends to form a 45.degree. angle and to assemble the lengths to form mitered corners. Due to the hollow construction of the metal extrusions, it has been necessary to add additional elements to the corners, such as gussets and the like, to permit screws, rivets, or other fasteners to be used to securely tie the corners together. The well-known miter joint is therefore dependent upon the gussets to provide strength and rigidity since the contacting surfaces of the extrusions provide little or no rigidity. Such construction requires additional manufacturing operations in producing the gussets and additional labor for installing the gussets during assembly.
There have been attempts made to provide a more rigid and stronger corner joint for joining such hollow extrusions. For example, in U.S. Pat. No. 4,143,493 to Booi, a window frame structure is disclosed in which the extrusions are abutted at the corners and the junction between the abutting frame members is accomplished by a screw in one member engaging a tongue in the other member. Although this construction is simpler to assemble than a mitered corner, it lacks torsional strength. While perhaps suited for window use, the joint would not be satisfactory for doors. In U.S. Pat. No. 3,166,163 to Wahlfeld, a corner construction is taught in which one extrusion includes a groove along a surface to be joined and the joining extrusion includes a projecting tongue which fits into the groove of the first section. The tongue is then welded to the groove. Although an improvement over Booi, assembly of the Wahlfeld corner requires a welding operation and the majority of torsional forces would be applied to a relatively narrow tongue portion of one element. Mendelsohn in U.S. Pat. No. 3,081,852 shows a window frame for a storm sash in which a partially abutting joint is disclosed. However, this patent discloses channel-type extrusions rather than the tubing-type extrusions with which the present invention is concerned.
Therefore, there is a need for a simple, strong and rigid corner joint construction for use with rectangular, hollow tubes which can be assembled with a minimum of material and labor.